g pa compri
Relis ton cours, cette formule y figure.
dacc merci mais comment on calculr pour le petit b
Il te faut repondre a la question a pour faire la b.
je l'ai ait mais la b je n y arrive pas

Réponses

2014-09-27T21:31:51+02:00
Exercice 43
a) Vect(AB) = (xB - xA ;  yB - yA)
Vect(AB) = (-2 - 1 ;  3 - 2)
Vect(AB) = (-3;1)

Vect(AC) = (xC - xA ;  yC - yA)
Vect(AC) = (4 - 1 ;  1 - 2)
Vect(AC) = (3;-1)

Vect(BC) = (xC - xB ;  yC - yB)
Vect(BC) = (4 +2 ;  1 - 3)
Vect(BC) = (6;-2)

b) 2Vect(AB) = 2(-3;1) = (2*-3;2*1) = (-6;2)  (* se lit multiplié par)
-Vect(AB) = -1(-3;1) = (3;-1)
1/2*Vect(AC) = 1/2*(3;-1) = (3/2;-1/2) = (1,5;0,5)
-Vect(AC) = -1(3;-1) = (-3;1)
2Vect(BC) = 2(6;-2) = (12;-4)
2/3*Vect(BC) = 2/3(6;-2) = (2*6/3;2*-2/3) = (4;4/3)

c)
2Vect(AB)+1/2*Vect(AC) = (-6;2) + (1,5;0,5) = (-6+1.5;2+0.5) = (-5.5;2.5)
-Vect(AB) + 2Vect(BC) = (3;-1) + (12;-4) = (3+12;-1-4) = (15;-5)
2Vect(AB)-Vect(AC)+2/3*Vect(BC) = (-6;2) + (-3;1) + (4;4/3)
2Vect(AB)-Vect(AC)+2/3*Vect(BC) = (-6-3+4;2+1+4/3) = (-5;3+4/3) = (-5; (9+4)3)
2Vect(AB)-Vect(AC)+2/3*Vect(BC) = (-5;13/3)